"No Wi-Fi adapter found" is different from "Wi-Fi does not connect". The first means the laptop cannot see the wireless card at all; the second usually means the card is present but something else is wrong — antennas, drivers, settings, the router. This guide deals with the first case: a card that does not appear on the bus. It covers what the card needs from the motherboard, how to check each requirement, and when the card itself is to blame.
Present but not working, or not present?
| Symptom | Meaning |
|---|---|
| No wireless adapter in the device list at all | Card not detected — this guide |
| Adapter listed with an error | Driver or firmware |
| Adapter works but sees no networks or weak signal | Antennas, connectors, radio disabled |
| Bluetooth works but Wi-Fi does not (combo card) | Wi-Fi part of the card, PCIe path or driver |
| Wi-Fi works but Bluetooth does not | USB path to the card, or driver |
Most laptop wireless cards are combination cards: Wi-Fi over PCIe, Bluetooth over USB. That split is useful — if one half works, the card has power, and the problem is in the other half's path.
What the card needs from the board
| Requirement | Typical signal or rail | What happens if it is missing |
|---|---|---|
| Power | 3.3 V, often switched | Card completely dead |
| PCIe lane | Transmit and receive pairs | Wi-Fi not detected |
| Reference clock | A 100 MHz differential clock pair | Wi-Fi not detected |
| Clock request | CLKREQ# or similar | Clock may never be enabled |
| Reset | PERST# or similar | Card held in reset |
| Radio disable | W_DISABLE# or similar | Radios off; usually still detected |
| USB pair (for Bluetooth) | D+ and D− | Bluetooth missing |
The PCIe link and the M.2 connector are covered in the glossary under pcie and m2 slot.
Step 1: easy checks
- Reseat the card and check that the screw holds it down properly.
- Try a known-good card of a supported type. This single test separates card faults from board faults.
- Check the BIOS for a wireless enable setting and for an airplane-mode or radio switch option.
- Look for a physical switch on older laptops — a slider or a key that disables wireless.
BIOS whitelists
Some older business laptops only accept wireless cards from an approved list. With an unapproved card they may stop at a message such as "unauthorized network card" or simply ignore it. If you replaced the card recently and the laptop then refused it, check whether that model has a whitelist before suspecting the board.
Step 2: power at the slot
With the laptop on:
- Find the 3.3 V pins of the wireless slot in the schematic. On an M.2 Key E slot there are several of them.
- Measure at the slot pins or the capacitors next to the slot.
On many boards, slot power passes through a load switch enabled by the EC or chipset. If the power is missing:
- Check the switch's input — is the source rail there?
- Check its enable signal — is the board asking for power?
- With the board unpowered, check the slot rail to ground for a short.
Step 3: reset and clock request
The card is held in reset until the chipset releases the reset line. With the laptop on and the card installed, the reset signal should be at its released level — for an active-low signal that is high. If it stays low, the chipset is not bringing up that PCIe port: check BIOS settings, the chipset's power-good signals and any series resistors on the line.
CLKREQ# is driven low by the card to ask for the reference clock. If it is stuck high because of a broken trace, the clock generator may never send the clock, and the card will not train its link. Check continuity of CLKREQ# from the slot to its source and its pull-up. The reference clock is a fast differential signal; a multimeter can only confirm the lines are not shorted or open. The clock itself is explained in clock signal.
Step 4: the PCIe and USB lines
With the board unpowered and the card removed, measure each PCIe and USB line at the slot to ground in diode mode. Lines of the same type should read similarly. Look for:
- A line near zero — shorted, perhaps a damaged chipset pin or a bridge at the slot.
- A line OL while its partner reads normally — broken trace, cracked via or missing AC coupling capacitor.
PCIe transmit lines from the chipset usually pass through small coupling capacitors near the chipset or slot. They are tiny and easily knocked off during repairs; check that they are all present.
Step 5: radio disable
The radio disable line does not normally hide the card; it switches the radios off. But on some laptops, an active disable line combined with a driver policy makes the adapter disappear from the network settings. Measure the line with the wireless switch or hotkey in each position. It should change state. A line stuck in the disable state usually comes from the EC, a switch or a corroded resistor.
Soldered wireless modules
Thin laptops increasingly have the wireless chip soldered to the board. There is no card to swap, so the same checks apply but deeper: the module's supplies, its reset, its clock and crystal, and its PCIe lines. A soldered module damaged by liquid or static often needs replacement with hot air and a matching part — a job that needs the exact part number from the schematic or the old chip.
The SSD connection
Wireless cards and NVMe drives use the same kind of link, and many checks are identical. If the laptop has both a missing SSD and missing Wi-Fi, look for a shared cause: a common clock generator, a shared power rail or chipset damage. The SSD side is covered in Laptop SSD or NVMe Drive Not Detected: Board-Level Causes.
Example: Wi-Fi gone after a keyboard replacement
A laptop lost its Wi-Fi after a keyboard replacement; Bluetooth still works, so the card has power and its USB side is fine. A known-good card is also not detected. With the laptop on, the card's reset line sits at its released level, but the clock request line measures high even with the card installed. With power removed, continuity from the slot's clock request pin to the chipset side stops at a tiny resistor next to the slot — knocked loose during the keyboard work. Refitting it restores the line, and the Wi-Fi adapter appears at the next boot.
FAQ
Why does Bluetooth work but Wi-Fi does not?
On combo cards, Bluetooth uses USB and Wi-Fi uses PCIe. If Bluetooth works, the card has power; the fault is in the PCIe path, the Wi-Fi half of the card, or the driver.
Can a BIOS setting hide the Wi-Fi card?
Yes. Many BIOSes can disable the wireless slot or radio. Some older laptops also reject cards that are not on their approved list.
Is it the card or the motherboard?
Try a known-good card. If it is detected, replace the original; if not, the board needs checking.
Can antennas cause the card to disappear?
No. Missing or damaged antennas cause weak or no signal, but the card still appears in the device list.
Can a dead wireless card stop the laptop from booting?
A card with a shorted supply can pull down a shared rail and affect other parts. Remove the card and see whether the laptop behaves differently.
Bottom line
A wireless card needs power, a released reset, a clock and working PCIe lines. Confirm card versus board with a known-good card, check 3.3 V at the slot and its switch, measure reset and clock request, compare the lines in diode mode, and remember BIOS settings and whitelists. The wifi module itself fails less often than the small parts and signals around it.